Electrical discharge apparatus

ABSTRACT

ELECTRICAL DISCHARGE APPARATUS INCLUDES AN ELECTRODE, A HOUSNG OF DIELECTRIC MATERIAL ENCLOSING THE ELECTRODE AND A TRANSFORMER HAVING ITS SECONDARY WINDING CONNECTED TO THE ELECTRODE. THE HOUSING IS FILLED WITH A HIGH STRENGTH DIELECTRIC FLUID SUCH AS OIL. TO ENABLE THE SECONDARY WINDING TO UTILIZE THE INSULATING PROPERITIES OF THE DIELECTRIC FLUID IN THE HOUSNG, AND AT THE SAME TIME PROVIDING ADEQUATE COOLING FOR THE TRANSFORMER CORE AND PRIMARY WINDING AND TO FACILITATE CHANGING FREQUENCY BY CHANGING THE CORE AND PRIMARY WINDING, THE HOUSING WALL STRUCTURE HAS A TUBULAR PORTION GOING THROUGH THE HOUSING AND ONE LEG OF THE LAMINATED CORE PASSES THROUGH THE TUBULAR WALL, WITH THE REMAINDER OF THE CORE OUTSIDE THE HOUSING, AND THE SECONDARY WINDING IS WOUND ON THE TUBULAR WALL PORTION WITHIN THE HOUSING, WHILE THE PRMIARY WINDING IS WOUND ON AN END OF THE TUBULAR WALL PORTION PROJECTING FROM THE HOUSING. THE HOUSING INCLUDES A FACEPLATE OF DIELECTRIC MATERIAL, SPACED FROM THE ELECTRODE AND INCLUDING A PLURALITY OF PARALLEL CONDUCTIVE BARS EMBEDDED IN THE MATERIAL EACH WITH BOTH OF ITS EDGES EXPOSED ON RESPECTIVELY OPPOSITE SIDES OF THE FACEPLATE, TO INSURE DISPERSAL OF THE CHARGE PRODUCED ON THE ELECTRODE.   D R A W I N G

Fab. 6; 1973 R. L. WILLIAMS 3 ELECTRICAL DISCHARGE APPARATUS Filed Sept-10, 1971 CONTROLS D O D v FIG. I. I3 fl: 2 1- 36 9 121-1 I/m 1-? 5 i;

4! F R R2 FIG.2. INVENTORZ RALPH L. ILLIAMS BY Ma ATTORNEYS.

United States Patent US. Cl. 204-312 14 Claims ABSTRACT OF THE DISCLOSURE Electrical discharge apparatus includes an electrode, a housing of dielectric material enclosing the electrode and a transformer having its secondary winding connected to the electrode. The housing is filled with a high strength dielectric fluid such as oil. To enable the secondary winding to utilize the insulating properties of the dielectric fluid in the housing, and at the same time providing adequate cooling for the transformer core and primary winding and to facilitate changing frequency by changing the core and primary winding, the housing wall structure has a tubular portion going through the housing and one leg of the laminated core passes through the tubular wall, with the remainder of the core outside the housing, and the secondary winding is wound on the tubular wall portion within the housing, while the primary winding is wound on an end of the tubular wall portion projecting from the housing. The housing includes a faceplate of dielectric material, spaced from the electrode and including a plurality of parallel conductive bars embedded in the material each with both of its edges exposed on respectively opposite sides of the faceplate, to insure dispersal of the charge produced on the electrode.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to apparatus for electrically treating plastic film to improve its surface adherency for inks and adhesives.

The prior art Earlier apparatus for treating plastic film and the like has utilized a simple arcuate plate electrode uniformly spaced from a grounded metal cylinder over which the film moved. In such apparatus, a coating of dielectric material is required on the grounded roll. Because of electrical strain, the dielectric coating has a short life and requires frequent replacement. Porosity of the dielectric coating permits the accumulation of air in the coating beneath the film being treated. The accumulated air ionizes due to electrical strain, and treats the under side of the film, which is generally undesirable because when so treated, separation of coiled film is rendered diflicult and in some instances impossible without damage to the film.

My patent, No. 3,484,363, discloses an electrode having a dielectric faceplate with a number of spaced pin-like conductors passing through it. The electrode housing disclosed in this patent contains a plate electrode surrounded by a fluid dielectric medium, and the transformer is entirely outside the housing and connected to the electrode plate by a conductor.

SUMMARY OF THE INVENTION The invention provides electric discharge apparatus including a transformer and having improved means for the dispersion of discharges comprising a plurality of conductive metal bars embedded in a dielectric faceplate, and in which the location of the transformer with its core passing through the dielectric-fluid filled electrode housing with its secondary coil in the housing utilizes the high dielectric strength of the fluid-filled housing to insulate 3,715,360 Patented Feb. 6, 1973 the high voltage of the secondary coil, the primary coil being located outside the electrode housing and preferably within an air cooling hood surrounding the housing, thus facilitating changing of the primary without opening the housing and utilizing the air current in the hood to dissipate the heat produced in the core by eddy currents and in the primary coil.

Objects of the invention accordingly include the elimination of dielectric coating on the grounded roll when the apparatus is used for creating plastic film, provision of an electrode structure offering improved discharge dis persion, and transformer arrangement in which the secondary winding enjoys the superior insulating characteristic of oil immersion, while the primary winding and all of the core are outside of the oil bath, and hence selectively changeable so as to facilitate changing the frequency without disturbing the secondary and the oil bath, and also capable of being air cooled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal vertical sectional view of electrical discharge apparatus embodying the invention, as applied in a plastic film treating apparatus.

FIG. 2 is a transverse vertical sectional view along line 22 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The letters R, R and R denote a series of metal rolls on the exposed machined metal surfaces of which a strip of polyethylene film F is carried. At least one of the rolls R is grounded at G to form an electrode for treatment of the film surface by a corona type discharge.

For providing a corona discharge, a self-contained electrode structure, generally indicated at 1, is located above roll R Electrode structure 1 comprises a housing 3 of dielectric material, preferably epoxy. Housing 3 includes a large shallow rectangular base portion having a flat horizontal bottom wall 5, top wall 7, side walls 9 and end walls 11.

The central portion of the top wall is extended upwardly in the form of upright side wall portions 12 and end wall portions 13, the latter merging at their upper ends with an arcuate top wall portion whose axis extends transversely of the electrode structure.

Along the axis of arcuate top wall portion 15, the housing is formed with a square section tubular wall portion 17 connecting opposite side wall portions 12, 12 and having open ends protruding from side wall portions 12.

The purpose of the upstanding central portion of housing 3 is to mount and partially enclose a transformer, the oval core of which has its bottom horizontal leg 19 extending through tubular wall portion 17, its top horizontal leg 21 extending over the top of arcuate top wall portion 15 and its arcuate ends 23 outward of side wall portions 12, 12. With this arrangement, the major part of core 19, 21, 23 is located outside of the housing where it may be air cooled, as will be described hereinafter. Core 19, 21, 23 is preferably formed of a plurality of laminae 20 detachably secured in lapped relation in upper leg 21 by bands 22, to facilitate removal and replacement of the core by pulling or pushing the laminae through tubular Wall portion 17.

To provide similarly for cooling of the primary winding 25 and to facilitate changing it, it is mounted on a protruding end portion of tubular wall portion 17 outside of and adjacent to housing side wall portion 12.

To provide for adequately insulating the secondary winding 27, it is mounted on tubular wall portion 17 within the housing upstanding central portion, and the interior of the housing is filled with a suitable liquid dielectric 29, such as oil, fed from an external reservoir 31 connected to the housing central portion by suitable conduits 3d.

The electrode comprises a metal plate 35 centrally positioned within the housing base and supported from top wall 7, by blocks 36 of dielectric material, in spaced relation with all the walls, 5, 7 and 9 thereof and parallel to bottom Wall A suitable electrical conductor 37 connects secondary winding 27 with electrode 35 to transmit high voltage currents from the latter to the former.

To provide for dispersal of discharge from electrode 35 into the treatment space adjacent to roll R in the form of a corona, housing bottom wall 5 includes a relatively thick faceplate 39, also of dielectric material, preferably polyethylene, bonded along its upper surface to the lower surface of bottom wall 5, and a series of parallel conductive metal bars 41 are embedded in the composite plate 5, 39 in parallel relation with each other, With their major surfaces normal to the plane of plate 5, 39 and with their edges slightly protruding from the upper and lower surfaces of plate 5, 39. Preferably the lower surface of plate 39 in the region above roll R is of shallow concave arcuate shape concentric with the axis of roll R and the vertical dimensions of bars 41 are varied accordingly to locate their lower edges equidistant from the periphery of roll R so as to provide uniformity in the intensity of the discharge received by film P.

All but the bottom of housing 3 as well as the protruding top 21 and ends 23 of the transformer core are surrounded by a sheet metal hood having a shallow base part with vertical side walls 43, top Walls 45, and end walls 47. The latter are spaced along their lower margins from housing end walls 11 at 4 9 to provide up-draft air inlets. The central portions 51 of end Walls 47 are extended upwardly to a higher level than the top leg of core 21, and are connected at their upper edges by a horizontal top wall 53. The vertical edges of end wall central portions 51, the side edges of top wall 53 and the inner edges of hood base top walls 4-5 are connected by vertical side wall portions 55 to complete the hood enclosing the transformer core, the primary winding 25 and the dielectric housing.

To provide for the circulation of cooling air through the housing, an upwardly directed exhaust duct 57 on hood top wall 53 is connected to exhaust blower 59, which draws air in through bottom inlets 49, and through the hood, past primary coil 25 and the exposed ends 23 and top leg 21 of the core to dissipate heat produced in the primary coil and the core.

Operation of the apparatus is as follows: Primary winding 25 is energized, and voltage of the desired magnitude is induced in secondary coil 27, which through conductor 37 energizes electrode plate 35. The high. voltage on plate 35 is transmitted by capacitance to the inner (upper) edges of bars 41 in faceplate 5, 39 and the charges received by bars 41 from electrode plate 35- are similarly transmitted by capacitance across the space between the bottom of faceplate 39 and roll R For treating polyethylene film the voltage and current provided by the secondary winding to plate 35 must be such as to produce a corona discharge from bars 41. As film F passes over the surface of roll R the discharge acts on the film upper surface, in known manner, to make that surface adherent to inks and adhesives. Because of the smooth impervious metal surface of roll R there are no air pockets between the film and roll R and hence no undesired treatment of the underside of the film.

During the operation as described above, the liquid dielectric medium 29 provides adequate insulation for the high voltages on secondary winding 27 and electrode plate 35. At the same time, exhaust blower 59 draws air from intakes 49, through the hood past primary winding 25 and the exposed ends 23 and top leg 21 of the core, to dissipate heat produced in the primary winding and core.

It it beco es neces a y or desira e to ch g he ou put of the transformer, this can be done without breaking the seal on the housing, by separating the core laminae at the top leg of the core, pulling them through tubular wall portion 17, changing the primary winding, and inserting the laminae of a different core through tubular wall portion '17, and uniting the laminae at the top by means of bands 22 The details of the apparatus disclosed herein may be modified substantially without departing from the spirit of the invention and the exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. Electrical discharge apparatus comprising an electrode, housing comprising wall structure surrounding said electrode, said wall structure including a tubular portion through a portion of said housing, a transformer including a core having one leg extending through said tubular wall portion with its other parts outside of said housing wall structure, a secondary Winding on said tubular wall portion within said housing, an electrical connection between said secondary winding and said electrode, and a primary winding surrounding a portion of said core outwardly of said housing.

2. Electrical discharge apparatus accord-ing to claim 1 wherein said tubular wall portion projects outwardly from said housing and said primary winding is mounted on said projecting part of said tubular wall portion.

3. Electrical discharge apparatus according to claim 2 wherein said core has another leg substantially parallel to said first named leg and end portions connecting said legs to each other, said other leg and said end portions being located outside of said housing.

4. Electrical discharge apparatus according to claim 3 wherein said core comprises a series of laminae removably secured at their ends in lapped relation outwardly of said housing wall to form a continuous core.

5. Electrical discharge apparatus according to claim 1, including a hood substantially enclosing said housing and generally in spaced relation with the exterior of said housing, and with said primary winding and the portions of said core outward of said housing, and means for circulating air through said hood.

6. Electrical discharge apparatus according to claim 1 wherein said electrode is a flat plate and said housing wall structure comprises a shallow fiat portion enclosing said plate and another higher portion in full communication with said shallow portion, said higher portion including said tubular wall portion and containing said secondary winding.

7. Electrical discharge apparatus according to claim 1 wherein said electrode is a flat plate and said housing wall structure includes a faceplate of dielectric material parallel to said electrode, there being a plurality of spaced apart conductors of substantially less area than the area of said faceplate passing through said faceplate.

8. Electrical discharge apparatus according to claim 7 wherein said conductors are parallel fiat bars with their major surfaces normal to the plane of said faceplate and their opposite edges exposed on opposite sides of said faceplate.

9. Electrical discharge apparatus according to claim 7 including a conductive roll having a smooth impervious surface in spaced relation with said faceplate and defining with said faceplate a reaction space between them, said faceplate being formed with a concavity of arcuate cross section concentric with said roll.

10. Electrical discharge apparatus according to claim 8 including a conductive roll having a smooth impervious surface in spaced relation with said faceplate and with its axis parallel to said bars, said face plate being formed with a concavity of arcuate cross section concentric with said roll and said bars being of different widths conforming to said concavity.

11. Electrical discharge apparatus comprising a plate electrode, a housing of dielectric material surrounding said electrode in spaced relation therewith and containing a fluid dielectric medium, said housing including a faceplate of dielectric material parallel to said electrode, and a conductive bar embedded in said faceplate with its major surface normal to the plane of said faceplate and its opposed edges exposed on opposite sides of said faceplate.

12. Electrical discharge apparatus according to claim 11 including a conductive roll having a smooth impervious surface in spaced relation with said faceplate and defining with said faceplate a reaction space between them, said faceplate being formed with a concavity of arcuate cross section concentric with said roll.

13. Electrical discharge apparatus according to claim,

11 including a plurality of said bars in parallel relation with each other.

14. Electrical discharge apparatus according to claim 13 including a conductive roll having a smooth impervious surface in spaced relation with said faceplate and with its axis parallel to said bars, said faceplate being formed 6 with a concavity of arcuate cross section concentric With said roll and said bars being of different widths conforming to said concavity.

References Cited UNITED STATES PATENTS JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner US. Cl. X.R. 

